1. Field of the Invention
The present invention relates to a developer container used for supplying a developer to a development device of an image forming apparatus such as an electrostatic copying machine, a printer, and the like; a process cartridge; and a developer sealing member used for the developer container.
2. Description of the Related Art
An electrophotographic recording apparatus is conventionally used for a printer, a copying machine, and the like.
In such an electrophotographic recording apparatus, a developer is used in a development device and consumed with proceeding of an image formation process, and thus the developer must be opportunely supplied to the development device. Although a developer container is used for supplying the developer, the developer container is also used as a developer container for supplying a developer to a copying machine or the like at a time, and a developer container for a process cartridge used in a printer of a terminal device of information apparatus such as a computer, a facsimile, CAD, or the like.
As material for the developer container, high-impact polystyrene (HIPS), acrylonitrile-butadiene-styrene copolymers (ABS), and the like can be used. As a sealing member for sealing an opening, an easy peel film comprising a sealant layer of an ethylene-vinyl acetate copolymer (EVA), a tear sealing member comprising a cover film and a tear tape, and the like are used.
A sealing method for the sealing member comprises sealing the sealing member to the surface of an opening flange of the developer container by heat sealing or impact sealing.
However, the use of a conventional developer container has the following problems:
(1) Pressure sealability (referred to as "sealability" hereinafter) of a seal has been increasingly required for distribution with a recent increase in size of the developer container. In addition, the number of grades of materials such as HIPS, ABS, and the like, which are used for the developer container, has been increased. Particularly, the number of grades with low sealability which contain a large amount of a seal inhibitor such as metal stearate or the like contained in a flame retardant or releasing agent, as in UL flame-retardant V2 grade HIPS, has been increased. There is thus demand for a seal with high adhesion which can be applied to these grades.
(2) Conventional sealant material EVA has a molecular structure in which a non-polar crystallizable methylene unit and an uncrystallizable vinyl acetate unit with high polarity are randomly copolymerized in its molecule. The sealability can be significantly improved by increasing the sealant content in the uncrystallizable vinyl acetate component. However, the sealant becomes sticky, and causes the problem of blocking (pseudo adhesion between films) in an original seal at high temperature and high humidity. This also causes a problem in that when a process cartridge is allowed to stand in the same environment of high temperature and high humidity, unsealing strength is significantly increased due to blocking between the sealant surface of a seal held between the container and a development frame and an end seal, thereby deteriorating operationality.
(3) EVA is produced by radical reaction of ethylene and vinyl acetate used as raw materials using a titanium catalyst (Ziegler catalyst) at a reaction temperature of about 200.degree. C. and a high pressure of 1500 atom or more. However, the Ziegler catalyst is a multi-site catalyst having many active points, and thus polyethylene comonomer cannot be uniformly polymerized with production a low-density component (sticky component) of low-molecular-weight polyethylene as a by-product. This results in the problem of easily causing the blocking phenomenon in the original seal and process cartridge.